The use of biometric identification systems is becoming ever more widespread for uniquely identifying people. The majority of known biometric identification systems use one or more intrinsic physical characteristics of a person for identification purposes. The accuracy of a biometric identification system is dependent on the uniqueness of the selected physical characteristic.
The iris is an example of a unique physical characteristic suitable for use in biometric identification systems to identify a person. Such biometric identification systems, generically referred to as iris recognition technology, have become increasingly popular. One advantage of this technology over other known biometric technologies, is that iris recognition technology has the smallest outlier (those user's who cannot use the system) group of all known biometric technologies. For this reason it is considered to be the most suitable biometric identification technology for mass use. Furthermore, due to the speed of comparison of iris recognition identification systems, it is the only known biometric technology well-suited for one-to-many identification.
Known iris recognition identification systems use pattern-recognition techniques to uniquely identify an iris pattern from a captured image of the irides of an individual's eyes. U.S. Pat. No. 5,291,560 discloses an example of a known iris recognition identification system, and describes in detail how such systems work. The article “How Iris Recognition Works”, published in IEEE Transactions on Circuits and Systems for Video Technology, Vol. 14, No. 1, January 2004, authored by John Daugman, who is incidentally the inventor of the afore cited patent, provides a discussion of the underlying principles explaining how iris recognition identification systems work.
As with other known biometric identification systems, iris recognition identification systems are also susceptible to fraud, and accordingly security features are required to mitigate against such threats. One shortcoming of known iris recognition identification systems, is that they are unable to accurately distinguish between a photograph of an iris and a real iris. Accordingly, it is possible to provoke a false positive identification result simply by presenting a suitably high-definition image of an iris for identification (i.e. for scanning) by an iris recognition identification system. In supervised environments, where the iris recognition identification system is operated by a human operator, this shortcoming does not present a cause for concern, since the operator supervises the iris image capture process, and can verify that a real iris is being presented to the iris recognition identification system. In contrast, this security shortcoming presents a significant cause for concern in unsupervised environments, where the iris recognition identification system is operated in the absence of a supervising human operator. In such environments it is relatively straightforward to deceive the iris recognition identification system into generating a false-positive match by presenting a photograph, or similar captured image, of an iris to the iris recognition identification system. This shortcoming of known iris recognition identification systems severely limits the diverse environments in which they may be used.
To date, there is no known solution to this problem. Known iris recognition identification systems are used almost exclusively in supervised environments. Where iris recognition identification systems are used in unsupervised environments, there is a high risk of the systems being defrauded. Improved security features are thus required for iris recognition identification systems to reduce the security vulnerabilities of such systems, in addition to increasing the diverse range of environments in which iris recognition identification systems may be securely operated. In particular, improved security features are required to enable iris recognition identification systems to be operated in unsupervised environments where it is not possible to verify prior to iris image capture, that the iris presented for image capture is a real iris instead of a pre-captured image of the iris.
It is an object of the present invention to mitigate for the above described security shortcomings inherent in known prior art iris recognition identification systems, and in particular to provide an improved security feature which enables iris recognition identification systems to be securely operated in unsupervised environments by being able to accurately distinguish a real iris from an image of the iris.